package Text_39;

import java.util.Scanner;

public class Code {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		System.out.println("请输入台阶数：");
		int n = sc.nextInt();
		double sqrt_5 = Math.sqrt(5);
        double fib_n = Math.pow((1 + sqrt_5) / 2, n + 1) - Math.pow((1 - sqrt_5) / 2,n + 1);
        System.out.println((int)(fib_n / sqrt_5));
	}

}
